The present invention relates to an electromagnetic focusing cathode-ray tube, and more particularly to an in-line type electromagnetic cathode-ray tube having an improved beam spot shape.
In an in-line type electromagnetic focusing cathode-ray tube, three in-line electron beams pass through a first grid and a second grid and are focused into narrow beams to form a so-called crossover, and they are then accelerated by an anode voltage and reach a fluorescent screen. On the other hand, a magnetic yoke made of a high permeability magnetic material absorbs magnetic fluxes emanated from a permanent magnet to produce focusing magnetic field one for each of the three in-line electron beams to form individual magnetic main lenses therein. In the prior art in-line type electromagnetic focusing cathode-ray tube, however, since a deflecting magnetic field control element is made of a high permeability magnetic material, it disturbs the beam focusing magnetic fields although it is arranged away from the permanent magnet much farther than the magnetic yoke. As a result, the beam spot on the fluorescent screen is flattened and focusing characteristics are adversely affected.